You'll have to run them through a relay, they will be far too high current to run from anything else.

Take a wire from the cigarette lighter, to a switch, to the relay.

Take a high current feed straight off the battery to the other side of the relay.

I fitted an aftermarket seat heater kit into my MK2 and it required about 30A with both seats on high heat

- take that from the cigarette lighter and you'll be popping fuses left right and centre!

I'm not sure what you're planning to do about switches

(retain the MK3 switches or fit custom ones) but you can easily wire an LED into the switch as well, so you know when you've left them on

(or more accurately, when your passenger has left theirs on

- it should be fairly obvious when yours is on!) which I did in my install.
